Vacuum interrupter having series connected resistor and shunting means for the latter

ABSTRACT

A vacuum interrupter employing a reciprocably movable contact has an opening and closing resistor in series circuit therewith and a knife switch is connected across the resistor to shunt it in and out of circuit. Two reciprocably movable operating members are connected at one of their ends to the movable contact of the vacuum interrupter and to the knife switch blade, respectively. The other ends of the two operating members are connected to cam slots in an actuating cam which is reciprocably movable transversely to the direction of movement of the two operating members. The cam slots are fashioned so that as the actuating cam is moved the vacuum interrupter closes before and opens after the knife switch.

[721 lnventor Richard (i. Brunner Dedham. Mass. [21] Appl. No 785,197 [22] Filed Dec. 19,1968 [45] Patented June 29, 1971 [73] Assignee Allis-Chalmers Manufacturing Company Milwaukee, Wis.

[54] VACUUM INTERRUFTER HAVING SERIES CONNECTED RESISTOR AND SHUNTING MEANS FOR THE LATTER 7 Claims, 1 Drawing Fig.

[52] US. Cl 200/144 AP, 200/144 B [51] lnt.Cl 1101b 33/16, l-lOlh 33/66 [50] Field of Search ZOO/144.2, 144APR1.145.748.153.121317/12 [561 A References Cited 5 UNITED STATES PATENTS 3,482,070 12/1969 Breitholtz et al. 200/144 X Primary Examiner-Robert K. Schaefer Assistant Examiner- Robert A. Vanderhye Attorneys-Thomas F. Kirby, Robert B. Benson and Lee H.

Kaiser ABSTRACT: A vacuum interrupter employing a reciprocably movable contact has an opening and closing resistor in series circuit therewith and a knife switch is connected across the resistor to shunt it in and out ofcircuit. Two reciprocably movable operating members are connected at one of their ends to the movable contact of the vacuum interrupter and to the knife switch blade, respectively. The other ends of the two operating members are connected to cam slots in an actuating cam which is reciprocably movable transversely to the direction of movement of the two operating members. The cam slots are fashioned so that as the actuating cam is moved the vacuum interrupter closes before and opens after the knife switch.

w w e b- VACUUM INTERRUPTEII HAVING SERIES CONNECTED This invention relates generally to closing and opening resistors used with vacuum interrupters. More particularly, it relates to means for operating a vacuum interrupter and a shunting switch for the resistor in a predetermined sequence.

' When vacuum switches (hereinafter called'vacuum interrupters) are used to switch capacitors in and out of an electrical power system, undamped transient oscillations occur in the system which cause severe system disturbances. It has been found that by using closing and opening resistors in circuit with the vacuum interrupters for current limiting purposes, the oscillatory RLC circuit may be critically damped, thus substantially eliminating the transients. The value of the resistors selected is a function of circuit parameters. In practice, the current limiting (opening and closing) resistor is connected in series with the vacuum interrupter and the resistor is shunted by a switch in a predetermined sequence with respect to operation of the vacuum interrupter.

Some vacuum interrupters employ a reciprocably movable contact which is connected to one end of a reciprocably movable operating member. The other end of the vacuum interrupter operating member has a cam follower which engages an offset cam slot in an actuating cam. The actuating cam is reciprocably movable transversely to the direction of movement of the vacuum interrupter operating member to effect movement of the vacuum interrupter to open and closed positions. It is desirable to provide an opening and closing resistor in series circuit with such a vacuum interrupter, to provide a switch in parallel with the resistor for shunting the resistor, and to provide means for operating theswitch in a predetermined sequence with respect to operation, of the vacuum interrupter.

In accordance with the present invention, there if provided a suitable support on which a vacuum interrupter of the aforesaid character is mounted. A resistor is mounted on the support and is connected in series with the interrupter, and a switch having amovable blade is connected across the resistor. A reciprocably movable operating member has one of its ends connected to the switch blade and the other of its ends has a cam follower which engages an offset cam slot in the actuating cam. The cam slot for the two operating members are so shaped that reciprocal movement of the actuating can causes the vacuum interrupter to close before and open after the knife switch.

OBJECTS It is an object of the present invention to provide improved means for switching capacitor banks in electrical power systems.

Another object is to provide improved switching means of the aforesaid character which employ opening and closing resistors to damp electrical oscillations in the system.

Another object is to provide improved means for switching resistors in and out of series circuit with a vacuum interrupter in a predetermined sequence with respect to operation of the vacuum interrupter.

Another object is to provide improved means of the aforesaid character wherein a vacuum interrupter employing a reciprocably movable contact has an opening and closing resistor in series circuit therewith and a knife switch is connected across the resistor, said vacuum interrupter and knife switch being operable in response to reciprocable movement of an actuating arm so that the vacuum interrupter closes before and opens after the knife switch.

Other objects and advantages of the invention will hereinafter appear.

DRAWINGS The accompanying drawing illustrates a preferred embodiment of the present invention, but it is to be understood that the embodiment illustrated in susceptible of modifications with respect to details thereof without departing from the scope of the appended claims.

In the drawing, the single FIG. depicts a side elevational view of switching means in accordance with the present invention.

DESCRIPTION OF THE INVENTION Referring to the drawing, there is shown switching means in accordance with the present invention for switching capacitors in and out of an electrical system and for critically damping system oscillations which occur during such switching. It is to be understood, for example, that the switching means is adapted to handle voltages of about 15 kv. or higher and currents on the order of 300 to 2,000 amperes. The switching means comprises supporting means such as a frame, support or housing 10 on which a hollow insulator 12 is mounted. A metal casing 14 is mounted on the end of insulator 12. A pair of hollow insulators 16 and 18 are mounted on one side of casing 14 and communicate with the interior of the casing. A line terminal 20 and a load terminal 22 are mounted on the outermost ends of the insulators l6 and 18, respectively.

A vacuum interrupter 24 is mounted within insulator l6 and comprises an evacuated envelope 26, a stationary contact 28, and a reciprocably movable contact 30. Stationary contact 28 is electrically connected to line terminal 20. Movable contact 30 is mechanically connected to one end of a reciprocably movable operating member 32 and the latter is provided at its other end with a cam follower, such as a roller 34. Operating member 32 extends into casing 14.

A resistor 36 is mountedwithin insulator l8 and is understood, for example, to be on the order of 50 to ohms. One end of resistor 18 is electrically connected to load terminal 22. The other end of resistor 18 is electrically connected to movable contact 30 of vacuum interrupter 24 by conductive means, such as an electrical conductor 38 located within casing 14.

Switch means are provided for shunting resistor 36 in and out of the circuit. Such means comprise a knife switch having a stationary contact jaw 40 which is electrically and mechanically connected to load terminal 22 and, therefore, to the said one end of resistor 18. Jaw 40 is adapted to engage with and disengage from a movable knife switch blade which is pivotably mounted on a suitable support member 44. Support member 44, which ismounted on casing 14 and is electrically conductive, is electrically connected to conductor 38 as at point 46. To insure a good electrical connection, an additional conductor 41 is connected between point 46 and blade 42. Thus, vacuum interrupter 24 is in series circuit with resistor 36 and the latter is shunted by the switch means when contacts 40 and 42 are engaged. Contact blade 42 is pivotably connected to one end of a reciprocably movable operating member 48 and the latter is provided at its other end with a cam follower, such as a roller 50. Operating member 48 extends through an opening 52 in casing 14. In the embodiment shown, operating members 32 and 48 are substantially parallel to each other and may be assumed to lie in substantially the same plane.

Operating means are provided for effecting operation of vacuum interrupter 26 and knife switch 39 in a predetermined sequence whereby the vacuum interrupter closes before and opens after the knife switch. Such means comprise the operating members 32 and 48, hereinbefore described, and further comprise an actuating cam, member or plate 54 which is located within casing 14 and is reciprocably movable therein along an axis which is transverse to the axes along which members 32 and 48 move. Cam plate 54 is movable upward and downward (with respect to the drawing) to open and closed positions, respectively, by a push rod 56 preferably made of insulating material, which extends through insulating column 12 into housing 10. It is to be understood that operating means for effecting movement of push rod 56 could be located within housing 10. Biasing means such as a tension spring 60 is connected between casing 14 and plate 54 to bias the latter to upward or normally open position in which the plate is shown.

Cam plate 54 is provided with cam means for effecting movement of the operating members 32 and 48 of the vacuum interrupter 24 and knife switch 39, respectively. The cam means comprise an offset slot 62 for engagement with cam follower 34 on operating member 32 and an offset slot 64 for engagement with cam follower 50 on operating member 48. As the drawing shows, the dimension A in slot 62 is smaller than the dimension B therein and the dimension C in slot 64 in greater than the dimension D therein. Thus, as cam plate 54 moves downward, operating member 32 moves to close vacuum interrupter 24 before operating member 48 moves to close knife switch 39. Thus, resistor 36 remains in effective series circuit with vacuum interrupter 24 for a short time after the vacuum interrupter closes. Conversely, when cam plate 54 moves upward, knife switch 39 opens to insert resistor 36 in series with vacuum interrupter 24 shortly before the vacuum interrupter opens. Such operation of knife switch 39 to shunt or connect resistor 36 in circuit effectively damps undesirable transient oscillations in a system wherein the switching means of the invention is employed. Distance of movement of cam plate 54, the length of time of such movement, the length of the slots 62 and 64, and other dimensions of the apparatus are variable and are selected and matched with respect to each other to provide a desired time delay of predetermined duration.

Although cam plate 54 is shown as having offset cam slots 62 and 64, it is apparent that other types of cam means could be employed. Furthermore, although rod 56 and plate 54 are shown as moving in a path substantially perpendicular to the paths of movement of the operating members 32 and 48, other directions of movement would be within the scope of the invention. Also, the operating members 32 and 48 could lie in different operating planes. Then too, the cam slots 62 and 64 could have different configurations than those shown to suit particular arrangements.

The embodiments of the invention in which an exclusive property or privilege l claim are defined as follows:

1. In combination,

a vacuum interrupter for switching capacitance in and out of an electrical power system,

a damping resistor in series with said interrupter,

a switch for shunting said resistor,

and operating means for closing and opening said interrupter and said switch, said operating means comprising: an actuating member reciprocably movable to open and closed positions,

an operating member for said interrupter,

an operating member for said switch,

each of said operating members being reciprocably movable in directions transverse to the direction of movement of said actuating member,

and cam means on said actuating member cooperating with cam means on said operating members for effecting closing movement of said interrupter operating member prior to closing movement of said switch operating member and for effecting opening movement of said switch operating member before opening movement of said interrupter operating member.

2. The combination according to claim 1 wherein said actuating member is substantially fiat and wherein said cam means comprises a plurality of slots in said actuating member.

3. The combination according to claim 2 wherein each of said slots comprise two offset segments, one of which is longer than the other.

4. in combination,

a support,

a vacuum interrupter mounted on said support and having a reciprocably movable contact rod,

said interrupter havin a pair of electrical connectors, a reclproca ly movab e interrupter operating member connected to said contact rod,

said interrupter operating member having a cam follower,

a resistor mounted on said support and having a pair of electrical connectors,

a shunting switch mounted on said support and having a pair of electrical connectors, a pivotable blade and a stationary contact for cooperation with said blade,

means for electrically connecting one of said electrical connectors of said resistor to one of said electrical connectors of said interrupter and to one of said connectors of said switch,

a reciprocably movable switch operating member connected to said pivotable switch blade,

said switch operating member having a cam follower,

and an actuating member on said support and being reciprocably movable in directions transverse to the directions of movement of said interrupter operating member and said switch operating member,

said actuating member having cam slots therein for cooperating with the cam followers to said operating members.

5. The combination according to claim 4 wherein said support comprises a housing,

a hollow insulator column on said housing,

and a casing on said column,

wherein said casing supports a pair of insulating housings in which said resistor and said vacuum interrupter are mounted, and wherein said actuating member is disposed within said casing.

6. The combination according to claim 5 comprising biasing means for biasing said actuating member to a predetermined position within said casing.

7. The combination according to claim 6 wherein said blade of said switch is mounted on said casing and wherein said stationary contact of said shunting switch is mounted on the insulating housing of said resistor. 

1. In combination, a vacuum interrupter for switching capacitance in and out of an electrical power system, a damping resistor in series with said interrupter, a switch for shunting said resistor, and operating means for closing and opening said interrupter and said switch, said operating means comprising: an actuating member reciprocably movable to open and closed positions, an operating member for said interrupter, an operating member for said switch, each of said operating members being reciprocably movable in directions transverse to the direction of movement of said actuating member, and cam means on said actuating member cooperating with cam means on said operating members for effecting closing movement of said interrupter operating member prior to closing movement of said switch operating member and for effecting opening movement of said switch operating member before opening movement of said interrupter operating member.
 2. The combination according to claim 1 wherein said actuating member is substantially flat and wherein said cam means comprises a plurality of slots in said actuating member.
 3. The combination according to claim 2 wherein each of said slots comprise two offset segments, one of which is longer than the other.
 4. In combination, a support, a vacuum interrupter mounted on said support and having a reciprocably movable contact rod, said interrupter having a pair of electrical connectors, a reciprocably movable interrupter operating member connected to said contact rod, said interrupter operating member having a cam follower, a resistor mounted on said support and having a pair of electrical connectors, a shunting switch mounted on said support and having a pair of electrical connectors, a pivotable blade and a stationary contact for cooperation with said blade, means for electrically connecting one of said electrical connectors of said resistor to one of said electrical connectors of said interrupter and to one of said connectors of said switch, a reciprocably movable switch operating member connected to said pivotable switch blade, said switch operating member having a cam follower, and an actuating member on said support and being reciprocably movable in directions transverse to the directions of movement of said interrupter operating member and said switch operating member, said actuating member having cam slots therein for cooperating with the cam followers to said operating members.
 5. The combination according to claim 4 wherein said support comprises a housing, a hollow insulator column on said housing, and a casing on said column, wherein said casing supports a pair of insulating housings in which said resistor and said vacuum interrupter are mounted, and wherein said actuating member is disposed within said casing.
 6. The combination according to claim 5 comprising biasing means for biasing said actuating member to a predetermined position within said casing.
 7. The combination according to claim 6 wherein said blade of said switch is mounted on said casing and wherein said stationary contact of said shunting switch is mounted on the insulating housing of said resistor. 